Guinness Irish Stew

oil
4 onions, chopped
10 oz mushrooms, quartered
3 stalks of celery, sliced
4 medium carrots, peeled and sliced
1 fist-sized turnip, peeled and diced
1 lb potatoes, peeled and diced
1 11.2 oz bottle of Guinness, stout if you can find it
4 cups veggie stock
2 heaping tablespoons tomato paste
2 teaspoons sugar
1 teaspoon salt - or more depending on stock
1 teaspoon grainy mustard
1/2 teaspoon pepper

Saute the mushrooms and onions until soft. Turn up the heat to high for a couple of minutes to get the pan really hot. Pour on the Guinness and let it cook for 2 minutes, stirring to get any brown bits off the pan. Add the remaining veggies and seasonings. Bring to a boil then let it simmer approximately 45 minutes or until the turnips and potatoes are soft.